Today's aircraft are often equipped with separate systems for providing emergency power and cargo fire suppression. It is known to use a ram air turbine for providing emergency power especially for a so-called “total engine flame out” (TEFO) situation or the loss of a main electrical power supply. Ram air turbines are capable for providing sufficient power when the speed of impinging ram air exceeds a certain minimum. However, this may be critical in a phase close to touch down during the landing phase of the aircraft.
As fire suppression systems or fire extinguishing systems for cargo compartments of an aircraft Halon fire extinguishers were often used. However, due to adverse effects of Halon for the ozone layer and as the commercial use of Halon will be limited by authorities, a replacement of Halon is necessary.
In civil aviation, potable water systems are well-known, which use on board water storage tanks for providing the quantity of water used in flight by passengers and crew and lavatories and galleys. It is known to generate potable water on board an aircraft by means of fuel cells under consumption of hydrogen and oxygen. However, this kind of water generation is directly coupled with the generation of electrical power. Hence, water will only be produced if the demand for electric power is sufficient.
In case air is used as an oxidant for said fuel cells, its oxygen content when generating water is depleted. If the remaining oxygen content in the cathode air is reduced to approximately 12% or less, this oxygen depleted air is usable for suppressing fire in case of a fire event on board or be used for fuel tank inerting or increasing safety in the fuel system. The depletion of oxygen is directly coupled with the demand for electric power and the stoichiometry in the fuel cell.